The surgical removal of tumors is one of the most important medical procedures in the treatment of cancer. Recently, radiopharmaceuticals have been developed which achieve improved specificity and efficiency for labeling malignant tissue and these improvements have generated a resurgence of interest in the use of hand held, intraoperative nuclear probes to provide in-situ information for the delineation of tumors. The probes which are presently available have proven extremely effective for certain types of lesions, but would be dramatically improved by the addition of imaging capability. In the Phase I program, the investigator conducted the basic research necessary to develop a new imaging surgical probe. The results of this research have lead to the assembly of a prototype imagining system which is capable of providing high resolution images in bone scintigraphy studies using rats. At present, the prototype is capable of providing images in real-time with about 2.5mm resolution. In Phase II, the investigator will conduct the research necessary to finalize the design of an imaging probe which will be capable of being used during surgery to delineate tumors in cancer patients. Such an improvement would allow the surgeon to visualize both the tumor itself and the area immediately surrounding it and to use his knowledge of anatomy to more easily explore the extent of the malignancy. Therefore, by the end of Phase II, a fully functional, high resolution imaging probe will have been developed and tested in clinical studies.